In my U.S. Pat. No. 3,780,073, which is incorporated herein by reference, the esters of the 3-oximes of DL-17.alpha.-ethynyl-19 nortestosterone and its derivatives having post-coital activity for the supression of fertility are described. Because it is generally desirable to administer the smallest effective dose of any drug, especially a steroid, considerable effort has been expended to resolve these esters in the expectation that the activity resides chiefly in one isomer. Thus it would be possible to administer a smaller dose of the active isomer and achieve the same result as a larger dose of the racemate. Prior to the present invention the active D-isomers have not existed free of the L-isomers. I have now found a method for preparing the D-isomers of said esters (wherein the activity of the racemic mixture chiefly resides) as pure chemical compounds free of the L-isomers.